Electricity plays a key role in modern society. It powers homes and businesses and keeps us comfortable by powering heaters and air conditioners. Most electricity that is generated is used to power lights and appliances for people around the world. This unit is designed to put students in the role of electrical engineers by providing them with experience in designing different circuit types and using a variety of electrical components, such as capacitors, transistors, and LEDs. Students learn the factors that affect the strength and direction of electric forces in circuits through several activities, online resources, and investigations. Students demonstrate understanding in a design challenge where they design and build a board game that incorporates circuitry as the basis of user interaction with the game.

Educational outcomes

Lesson 1: Students learn the importance of electricity and write a narrative about a world without it

Lesson 2: Students investigate and explain the role of electrons in producing electric forces

Lesson 3: Students build series and parallel circuits and explain observations in terms of electric forces

Lesson 4: Students use the attributes of diodes to control electric current flow through a parallel circuit

Lesson 5: Students build two LED circuits and explain observations in terms of electric forces

Lesson 6: Students read resistance color code values and build LED circuits having different resistors

Lesson 7: Students build an LED circuit that includes capacitors and resistors of different values

Lesson 8: Students build circuits that include transistors and other electrical components

Design Challenge: Students design, build, and test a board game containing circuitry that creates light and sound as evidence of energy transfer

STEAM INTEGRATION

Students observe electrical phenomena in circuits built with a variety of electrical components throughout the unit. They ask questions and investigate the factors that affect the electrical forces in each type of electrical component (MS-PS2-3). Students conduct an investigation to provide evidence that a electric fields and forces exist and can be relatively measured. (MS-PS2-5). Students learn how electricity is generated and sent through transmission lines for consumer use and then write a detailed narrative describing a world without electricity, providing an opportunity to practice writing skills. The culminating design challenge actively engages students in the design process and provides opportunities to apply prior knowledge and content from multiple subject areas to create an energy transfer device (MS-PS3-3).

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Unit Materials

This unit can be completed using RAFT’s Electrical Engineering Game Board Challenge kit or the following electrical components and reusable materials:

Design Thinking Overview

Our design thinking units have five phases based on the d.school’s model. Each phase can be repeated to allow students to re-work and iterate while developing deeper understanding of the core concepts. These are the five phases of the design thinking model:

EMPATHIZE: Work to fully understand the experience of the user for whom you are designing. Do this through observation, interaction, and immersing yourself in their experiences.

DEFINE: Process and synthesize the findings from your empathy work in order to form a user point of view that you will address with your design.

IDEATE: Explore a wide variety of possible solutions through generating a large quantity of diverse possible solutions, allowing you to step beyond the obvious and explore a range of ideas.

PROTOTYPE: Transform your ideas into a physical form so that you can experience and interact with them and, in the process, learn and develop more empathy.

TEST: Try out high-resolution products and use observations and feedback to refine prototypes, learn more about the user, and refine your original point of view.

NGSS MS-PS2-3: Ask questions about data to determine the factors that affect the strength of electric and magnetic forces.

NGSS MS-PS2-5: Conduct an investigation and evaluate the experimental design to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact.

NGSS MS-PS3-3: Apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy transfer.

Suggestions for pacing and differentiation

Adjust the time spent on each lesson according to student familiarity with electronics. Frequently revisit the static investigation and kinesthetic model, focusing on electron movement due to different charges (see Lesson 2). This provides the foundation for understanding how electric current interacts with different electrical components in circuits.

The lessons in this unit require students to connect different electrical components in circuits similar to the way electrical engineers would do using a common breadboard for prototyping. There are size and motor skill limitations to consider when using traditional breadboards and having multiple wires to follow and connect can be very confusing! We developed a method for breadboarding that uses cut pieces of “egg crate” foam to create component blocks. These blocks are labeled with the schematic symbol for each electrical component and the physical component is attached directly to the block on top of its schematic symbol. These blocks are able to be moved around easily and can be positioned on a larger sheet of the same egg crate foam, addressing the issues of size, motor skills, and confusion associated with using traditional breadboards. The power supply used for this unit is a battery pack consisting of two AA batteries arranged in series to produce three volts (see assembly instructions below). There will be certain circuits students will build that will require up to 6 volts, which can be achieved by assembling two of the 3V battery packs.

Cutting the Egg Crate Foam (one sheet per group)

The foam is textured with numerous “hills” and “valleys” that are very useful in keeping the electrical component blocks (described below) in place. It is ideal to cut the rectangular foam so that the underside of each block has a centered hill or valley.

The shorter side of the rectangular foam sheet is 24 cm long. Cut the foam sheet into strips that are 24 cm x 5 cm. This can be done using scissors, although a paper cutter would be better to ensure a straight cut.

Cut each foam strip into squares that are 5 cm x 5 cm, making sure the textured side of each square block has either a hill or valley.

Set the foam blocks aside.

Print and cut out the schematic symbols from the first page of the Symbol Blackline Master. Set aside the symbols for the incandescent bulb, battery (3 volts), and Component Circle. These will NOT be used as part of a foam component block.

Preparing the Component Blocks

Group the symbols of like components by creating separate stacks, one stack per component. Make sure the symbols are oriented the same way in each stack (see below).

Notice on each symbol there are bold dots. These indicate places where a hole will be poked through the symbol using a pushpin.

Lay a stack over the end of the cork provided. Poke through each bold dot on all of the symbols in the stack at one time. Do this for the remaining stacks.

Remove one symbol from a stack and position it on the flat side of a foam block.

Secure the symbol to the foam block using double-sided tape or glue (let it dry for a few minutes if glued).

Repeat for the remaining symbols except those set aside.

Mounting Electrical Components onto the Blocks

The leads of the electrical components can be easily bent using the cork as shown. This will help the leads to better insert into the foam blocks. The spacing between the pushpin holes on the symbols intentionally matches the width of the provided cork.

Diodes:

Diodes are electrical components discussed later in the unit. Mounting diodes onto their associated schematic symbols is relatively easy.

Bend the diode leads using a cork as shown below.

Note the diode has a noticeable marking on one side. This is indicated on the schematic symbol. Mount the diode onto its foam block as shown, making sure the marking is on the correct side.

Press down and insert the diode leads into the foam until the diode is firmly mounted and does not fall out.

Repeat for the remaining diodes.

Light Emitting Diodes (LEDs):

These components are diodes that emit light when sufficient electric current flows through them. They are mounted onto a foam block in a similar manner as the regular diodes. LEDs have one lead that is longer than the other (see below). The hole on the LED symbol into which the longer lead is inserted on the foam block is clearly indicated on the symbol.

Bend the LED leads using the cork.

Insert the leads into the correct holes on the symbol. Mount the LED, pressing down firmly.

Repeat for another LED.

Combined Component: 1K Resistor + LED

This component block will include a resistor with a value of 1K, that is, 1000 Ohms (covered later in the resistor lesson) and an LED. The resistor has colored bands to indicate the amount of resistance it adds to a circuit. The 1K resistor will either have four color bands or five colored bands. If it has four bands they will be brown on one end, black, red, and then gold (see below). If it has five colored bands they will be brown on one end, then two black bands, another brown, and then gold. Notice that the symbol for this combined resistor-LED component block contains both a resistor symbol and the LED symbol. The LED is positioned in the combination such that its longer lead is on the positive (+) side of the LED symbol.

Twist the longer lead of the LED around one lead of the 1K resistor as shown. It does not matter which lead of the resistor is twisted onto the LED lead.

Insert the remaining lead of the resistor and LED into the Resistor + LED foam block.

100 uF Capacitor

Capacitors are electrical components that store energy/charge. They come in a variety of shapes and sizes depending on the amount of energy they are designed to store (covered in a later lesson). The attribute of energy storage in capacitors is called capacitance, which is measured in units called farads (symbolized with an F) after the scientist Michael Faraday. Most capacitors will have the capacitance printed on them along with a voltage. In this unit there are several capacitors with unique values that can be used by students, one of them of particular interest is the 100 uF (microfarad) capacitor pictured below. Just as with the LED, this capacitor has one lead on the positive side that is noticeably longer than the other. The component symbol clearly indicates where this lead is to be inserted into the foam block.

Insert the leads through the holes on the schematic symbol for the 100 uF capacitor.

Press down to firmly mount the component into the foam block.

10K and 47K Resistors

Recall from above that resistors have colored bands on them to indicate the amount of resistance they provide in a circuit. For many circuits that can be built in this unit there are two resistance values that will be useful, 10K and 47K. If these components are labeled with five color bands, the bands will be as indicated below. Note the components are mounted to the foam blocks the same as the diode except that with resistors there are no positive or negative leads, meaning they can be inserted into either side of the component symbol.

10K = Brown, Black, Black, Red, Brown

47K = Yellow, Purple, Black, Red, Brown

Transistors

Transistors are electrical components that act as both switches and amplifiers in electrical circuits, meaning they can prevent current from flowing as well as making an electrical current larger. They have three leads called the base, collector, and emitter, abbreviated as B, C, and E on the schematic shown below. There are NPN transistors and PNP transistors (covered in more detail in a later lesson). It can be difficult to distinguish between these two types just by looking at the components but they do have numbers printed on them that can be useful for telling them apart. PNP transistors often have the code 2N 3906 whereas NPN transistors have 2N 3904. The pictures below show a PNP transistor. Notice on the provided schematic symbol that the orientation of the component is such that its flat side is to the right (see the pencil tip in the picture). Also notice that for both PNP and NPN transistors the center lead is the base lead (near the B on the schematic symbol).

Bend the transistor leads forming a tripod as shown above.

Insert the leads into the corresponding holes on the component foam block, pressing down firmly.

Repeat this procedure for the NPN transistor, making sure to use the NPN schematic symbol.

Assembling the 3V Battery Pack

Cut two 3.5 inch segments from the bubble tea straw. Next, cut one side of each segment along its length, as shown. The segments should open as shown.

Wrap one straw segment around one AA battery, noting the position of the positive battery terminal. Slide the battery towards the end of the straw segment. Wrap another AA battery in the same straw segment, making sure it is oriented the same as the previous battery.

Stretch a rubber band around the length of the assembly. Wrap the remaining straw segment around the assembly such that it wraps around the slit in the first straw segment and one part of the rubber band. The other part of the rubber band should be outside the assembly.

Place a paper clip between the rubber band and one battery terminal, as shown below. Repeat for the other terminal.

Note: This battery pack is a 3V power supply. Connecting two of these battery packs in series will produce 6V, which will be necessary for more complicated circuits. Series circuits are covered later in the unit.

Teacher Notes

Allow students to prepare the component blocks and battery pack. This can help them remember the schematic symbol for each electrical component. Point out to students that the battery pack is a series connection between two batteries, with each of their 1.5 voltages adding to produce a 3-volt output.

The Component Circle is an important inquiry tool used in this unit. It allows students to explore the effects of different resistance and capacitance values on the flow of electric current through circuits they will build later in the unit. The collection of resistors has a range of values (10R – 1M ohms) and acts as a variable resistor (covered later) that students can put into circuit at specific values, as opposed to actual variable resistors that would only allow students to observe the effects of relative amounts of resistance in the circuit. In other words, this allows students to draw inferences based on observations at specific resistance values. Similarly, the capacitors in the Component Circle have values ranging from 0.01uF – 470uF. Capacitors store electrical energy and this range allows students to observe the effects of specific capacitance values on their circuits. The Component Circle provides teachers and students with a practical method for storing electrical components and can easily be turned into an activity where students practice identifying components of different types and values.

Component Circle Assembly

The foam used for the Component Circle is a short cylinder with a vertical groove cut into its side. When viewed from one of its flat faces, the foam almost resembles a “Pac-Man” with a small mouth. The mouth-like groove is used to stand the Component Circle on a flat surface. Below are the assembly steps for the Component Circle.

Teacher Notes

The resistors in the kit should be sorted by resistance value and/or labeled. If this is not the case, it may be necessary to determine the resistance values for each resistor by reading the color code before putting them on the foam. The capacitor values should be written on the components in microfarads (uF), although it may be very small print!

In this lesson, students will learn about the impact of electricity on human labor and the environment. Students will watch a video on the relationship of electricity and energy, accompanied with a Q and A to establish the prior knowledge needed for the later lesson in this unit.

Essential Questions:

What is electricity?What is energy?

In what ways is electricity created? How does electricity delivered to us?

In what ways does electricity impact our lives and the environment?

LESSON PROCEDURE:

Any teacher directions not given in the sidebar go here before Student Directions

1. Introduction:

Turn off all electricity in the room to create an environment without electricity. If possible, turn off all devices and battery operated devices for full immersion.

Have students work in groups, assign each group a segment of society (such as health, transportation, communication, technology, sports, and entertainment), have each group write a creative fiction about that segment of society operating without electricity. Remind students to imagine the who, what, when, where, why, and how.

3. Reflection:

Reflect with students on why electricity is so important to our world.

Guiding reflection questions:

Why is electricity so important?

In what ways, does electricity support our daily lives?

After reflection, ask students if electricity is so important, what is it?

4. Share Media: Electricity is Energy.

Show RAFT’s animation on electricity and energy. This video connects the relationship between electricity and other forms of energy.

Recap and ask students what is energy? What needs to flow to produce electricity? How many different forms of energy exist including electricity?

5. Share Media: Electricity Generation

Get class to agree that when electrons flow, it causes electricity. Then ask how do we as a society produce enough flow of electrons to power our world?

Show Energy 101, Electricity Generation on Youtube. [This video explains how electrical energy is created and moved into our familiar homes and schools.]

6. Q and A: Environmental Impact

Ask students what are “the positive” effects and “the negative” consequences with each method of energy production? Ask students how and why pollution impacts the earth?

Sketch assessment: Divide students into groups, assign each group an energy source (Solar, coal, natural gas, nuclear, wind, water) and ask each group to sketch out how that energy source is produced and is transferred to their electrical outlet at home.

Online Group Quiz: Have student play a game of Kahoot for an online assessment. [See example on side tab]

Sample teacher and student dialog. Include reference to Maker Journal page and button to link to student maker journal page.

1. Introduction:

T: Okay everyone, we’re going to take some time and unplug. We’re going to turn off everything in this room that has electricity and have a chat. If electricity just went again tomorrow (no one has electricity anywhere), what would the world look like?

S: The things we have wouldn’t work. Like our phones, our stuff. [Accept all answers from students.]

T: We are going to take a moment, and write in groups. Each group will be assigned an area of society, and you will have to imagine what the area would look like if the world went dark and there was no electricity. Some of those areas include: telecommunication, financial institutions, transportation, sports, internet, schools, and public safety.

2. Group Writing:

T:Ok, everyone. Remember when writing your story to think of the who, what, when, how, and especially the when and how. If you have questions, start by asking and discussing with your group members, and if you still don’t know, ask an adult.

3. Reflection:

T: [Have groups share out their ideas.] We heard so many creative stories today. My question is what are some themes that all our stories have in common? In what ways, does electricity support our daily lives?

S: Electricity is in almost everything we do. It supports the classroom, our home, places we go, keeps us warm.

T: How would our lives be different in a world without electricity? In terms of the work we have to do to make a society function, what would be different?

S: People could die, nothing would work, it would be dark at night. We would have to do everything in the morning with sunlight, or in the full moon. People would have to work different, less driving from places to place. Things would just be much harder.

T: Is it safe to say that electricity plays an important part in a society?

S: Yes.

T: I am glad we can see that electricity is a big part of how our world works, but if it’s so important, then what is it?

T: Electricity is a form of energy, there are other forms of energy. To understand how it works, and how we as a society produce electricity, let’s watch these videos.

4. Share Media: Electricity and Energy

T: Let’s review some of what we just saw. So what is energy? What types of things have energy? How is electricity related to energy?

S:Energy is the ability for something to move. Energy is pretty much everywhere, and in everything. Things that don’t move still have chemical energy. Electricity is a part of energy, it is when electrons move.

T:At the atomic level, what happens with atoms and their components that give us electricity? The flow of ______ gives us electricity? and when they flow, where do they flow?

S:Electrons have to flow from one atom to the next to produce electricity.

5. Share Media: Electricity Generation

T: What process do we as use to generate a flow of electrons and produce electricity? Are the processes all the same? In what ways are they same and different?

S:We burn things. By burning things we can move motors and they help start the flow of electricity. Sometimes, we don’t burn things, and we use the power of the wind to start the motors.

T: Let’s watch this video to see what systems we have engineered to produce flow of electrons, especially at a large enough scale that electricity is provided for the majority of people living on earth. [Show video]

T: [Take questions and provide questions for Q and A] There are certain ways we make electricity that cause pollution, I am curious because in many way, this topic will direct impact your lifes, what are your thoughts on pollution? What are these byproducts that cause harm to the earth? How are people working to address environmental issues? Are there sources of clean electricity production?

S: The byproduct is pollution, and it is warming the earth. [Accept most answers.]

T: We are going to work in groups now. You will each be assigned an energy source such as wind, solar, nuclear, coal, etc, and as a group, you will have to sketch how (from that original energy source) is electricity made, and how it is delivered into our classroom right now.

Electricity is everywhere, and the modern world can not function without it. Our scientific endeavor to understand electricity has shaped the world economically and environmentally. It has also lead to discoveries in a wide range of fields including communication, medicine, and technology.

Electricity is caused by the flow of electrons. Electrons flow when introduced to magnetic fields. An electric generator works when a magnet spins and rotates its’ magnetic field through a coil of copper wires. There are different ways to spin a magnet, but most will use the mechanical principal of wheel and axle (one of 8 simple machines). Both fossil fuels and nuclear power create heat to boil water and produce steam which spins a turbine (or fan blades) to spin a magnet. Wind power bypasses boiling water to produce steam, and spins a magnet directly with wind power. Dams use the power of falling water to directly spin turbines as well.

Maker Journal Pages

Teacher Notes

Use different creative writing techniques to get your students to embrace story-telling and creativity such as writing a script for a favorite TV show, write from the first person perspective, switch writers every paragraph, create a graphic story.

Active Classroom

Makerspace integration: If there’s a makerspace at your site, integrate hands-on engineering with creative projects that might include set-design, painting, digital art, green-screen videos, and dioramas of a world without electricity.

Tech integration: Students who are familiar with coding in Scratch can also make animation or games that trace how electricity is produced.

Allowing students to self-select their projects will give them a sense of ownership and generate more excitement.

Communication is critical in the design process. Students need to be allowed to talk, stand, and move around to acquire materials. Help students become successful and care for the success of others by asking them to predict problems that might arise in the active environment and ask them to suggest strategies for their own behavior that will ensure a positive working environment for all students and teachers.

Learning Targets

MS-Ps1-3. Gather and make sense of information to describe that synthetic materials come from natural resources and impact society.

Cross-Cutting Concept: Interdependency of Science, Engineering, and Technology. Engineering advances have lead to important discoveries in virtually every field of science, and scientific discoveries have lead to the development of entire industries and engineered systems.

“Unpacked” components of the standard. (bullet format)

Students will be able to understand the impact of electricity on human society.

Students will be able to trace how natural resources is turned into electricity.

Students will build empathy for how electricity is made, and the environmental consequences of energy production.

Assessment

Student Self Assessment

Use the following Kahoot assessment to model your group survey. Students can take this individually or in small groups, but every class will need a way of connecting to the internet. This is meant to be a formative assessment.

Teacher Assessment

Review student makerspace journal pages for formative assessment and discuss with individual groups as they work.

Students use web resources and engage in activities to learn about atomic structure and the role electrons play in causing electric forces (MS-PS2-3). Students experience these forces first-hand by following a multi-step procedure to assemble a static-powered merry-go-round and then use it to observe the effects of charge imbalances generated by rubbing different materials together.

Essential Questions:

How are charges affected by electric forces?

What are electric fields? How might we investigate their existence?

LESSON PROCEDURE:

Web Research:

Review and discuss the steps for conducting safe and responsible internet searches for information (see Teacher Notes). A question you might ask students: “What should the end of a credible website URL look like if we want to know scientifically accurate information?” (Nudge them towards sites ending in .edu or .org. Sites ending in .com are okay if references are cited for the information contained in the site and/or the author is an expert in the content).

Students are to conduct research to find information on free electrons, charges, electric forces, and static electricity. The web resource listed in the External Resources section are a good starting point.

Students record websites and notes for each term in the Maker Journal page.

Modeling Electric Charges and Attractive & Repulsive Forces:

Create a large space in the room or take the class outside for a kinesthetic modeling activity. The space should accommodate the entire class.

Print the Electric Charge Labels and distribute one to each student. Some of the labels are positive while others are negative. Designate one student with a negative charge label to be the “test charge.”

Have students arrange themselves in any configuration they want within the designated space, making sure they hold up their labels for all to see.

Have the test charge student start at one end of the configuration and begin walking through the configuration of students (“charges”). The student should walk towards positive charges to model attractive forces and away from negative charges, modeling repulsive forces. During the first attempt be sure to clarify and correct the electric interaction as necessary.

Let’s get more dynamic! Have all students move within the designated space at once (recommend a relative speed as necessary). The student acting as the test charge, which could be a different student, now has a more challenging role as he/she must recognize the movement of the surrounding negative and positive charges and behave accordingly!

Conduct a think-pair-share engagement structure around these questions: “How was the test charge affected by electric forces in this model? Allow students to individually think (1-2 min) and write in the Maker Journal page. Pair them up and let them discuss their thoughts (2 min). Each pair shares their ideas with the group (1-2 min).

Investigation – Detecting and Analyzing the Presence of Static Electric Fields with a Merry-Go-Round:

Student groups gather the required materials (see Teacher Notes) and follow the instructions in the Maker Journal page to assemble the devices.

Students use different materials to generate charge imbalances and then observe their effect on the device, noting the relative amount of electric force causing the device to spin. Students should the relative distance between the interacting materials. For example, students may notice that rubbing the foam with fabric against a piece of plastic may effect the device from farther away compared to rubbing it a different material. Students record their observations for each material in the Maker Journal page.

Formulating an Hypothesis:

Student groups discuss their observations for each material, focusing on how their observations demonstrate relative differences in strength of the electrical forces involved in rotating the merry-go-round.

Groups brainstorm possible reasons for the relative differences in electrical force strength based on the attributes (characteristics) of the materials used in each observed interaction. Use the frame “I think _____ caused _____ because …” This helps students consider and practice using cause and effect relationships to predict phenomena within systems.

Groups develop a testable hypothesis on the existence of electric fields as demonstrated using the merry-go-round. They write down the hypothesis in the Maker Journal page.

Sample teacher and student dialog. This sample demonstrates how facilitators can have students experience phenomena either first hand or through media representations. It also provides an example of how to connect instruction to the students’ home, neighborhood, community, and/or culture. Notice in the example how students have opportunities to connect their explanation of a phenomenon to their own experience.

T: Show students images of the effects of static electricity. You may select images from a Google image search on the topic. Click here for one example. “What is causing this phenomenon? How might we investigate its cause?”

T: “Great ideas! This example serves as an initial observation and now we can investigate the phenomenon, but we might need some information so we can understand what we are investigating. We might need to find information on atoms, electrons, electric charges, electric forces, and types of electricity. This might help us find a cause for the phenomenon shown in the picture. Where might we find this information and more?”

S: “Google, Wikipedia, image search, library.”

T: “After we conduct our research, we will investigate the existence of electric fields using a static merry-go-round as a tool. Then, we will use what we learn to come up with a testable hypothesis that explains the existence of electric fields and explains the phenomenon we saw in the images.”

Atoms are the building blocks of all matter. There are hundreds of different atoms that combine to form molecules, becoming everything that we see and touch. They are VERY small but in order to understand electricity it is necessary to go even smaller, into the realm of subatomic particles.

There are three main subatomic particles: electrons, protons, and neutrons. Protons and neutrons form the nucleus of an atom. Electrons orbit around the nucleus, although not in nice circular orbits like planets. Instead, they quickly buzz around the nucleus in a space called an electron cloud. It is easier to understand electricity in terms of the familiar atom model that has the nice circular orbits, called the Bohr model of the atom (see below).The number of protons in an atom determines its atomic number. This number is one of the main pieces of information people see when looking at a periodic table. Boron, pictured above, has five protons and has an atomic number of five. Stable atoms have the same number of electrons as protons, meaning boron has five electrons. Neutrons keep the protons in the nucleus. The number of neutrons can vary, which is why atoms can have other forms called isotopes.

All matter has something called charge that is measurable. Charges are either positive or negative. Protons have a positive charge while electrons have a negative charge. Neutrons have no charge (neutral). Protons attract electrons because they have opposite charges. Protons repel other protons because they carry the same charge (see below). Electrons behave in much the same way towards other electrons. The force doing the attracting and repelling, or pulling and pushing, is called the electrostatic force. Electrons are attracted to the nucleus of an atom because it contains the positively charged protons. Electrons that are closer to the nucleus of an atom feel a stronger electrostatic force towards the nucleus than those further away from the nucleus. The distance between the charges greatly affects the electrostatic force generated between them, whether it is an attractive force or repulsive force!

When the outermost electrons in an atom, called valence electrons, experience a strong enough electrostatic force, they can be bumped away from the atom. These electrons are free electrons because they travel through free space. Remember that atoms are so small that there is space between them, even in solid objects. The bumped electrons can be continuously attracted and repulsed along in a particular direction by electrostatic forces. This is a chain-like electron flow called electric current. Without electrostatic forces there would be no electric current. In the image below, the valence electron in the left-most atom is being bumped to the adjacent atom to the right, so in this example the attractive and repulsive electrostatic forces are pushing the electron from left to right.

The electrostatic forces pushing and pulling the electrons are generated by an electric field. Electric fields are models of physical interactions between objects of charge, just like a gravitational field is a model of the interaction between objects of mass (e.g., Earth and the Moon). Notice below that the field lines indicate the charges are attracted to each other. Had the red charge been a positive charge the field lines would point away, indicating a repulsive interaction. The difference between these models is that in electric fields the charges can move towards or away from each other whereas with gravity objects of mass only move towards each other. We cannot see electric fields just as we cannot see gravitational fields, but we can see the real effects they have on objects. It is relatively easy to provide evidence of the existence of electric fields by rubbing different materials together to generate static.

Touching two items together and then separating them can move electrons from one item to the other. The item that gains electrons will have a net negative (-) charge if the item has more electrons than protons. The item that loses electrons will have a net positive (+) charge if the item has fewer electrons than protons. When a balloon is rubbed on a person’s hair, for example, the balloon has a strong affinity for electrons and acquires more electrons from the hair. This gives the balloon a net negative charge. Meanwhile, the hair strands that have lost electrons to the balloon have a net positive charge (see image below). The opposite net charges are attracted to each other. Note that electrons are moved, not created, in this process. Charges will “stay put” unless the item is a conductor that lets electrons move about easily. An item with a net charge (positive or negative) is said to be charged or to have a charge imbalance. Different materials vary in how strongly they “hold on” to electrons. For solid materials the positive charges (protons) cannot leave or move about like the electrons.

External Resources

Maker Journal Pages

Teacher Notes

Conducting Web Research

Model good techniques for safe quality internet searches. Consider pre-selecting sites that yield quality information on atomic structure, electric forces, static electricity, and fields. Sites having .edu or .org are often more reliable for accurate information on a topic. Sites ending in .com tend to be focused on specific products to be sold to a consumer and therefore the information can be biased.

Static Merry-Go-Round Materials

Remove the items listed below from the RAFT Static Merry Go Round kit and place them on a cart or large tabletop. Cut 10 Mylar sheets in half to make 20 pieces that are 1.25″ x 1.5″. Cut the straws in the kit in half, making 10 half straws. Each group needs to gather the following materials:

1 straw half section

Wood screw

Stiff foam base

Pushpin

Sports bottle cap]

Reflective Mylar® sheets

Rubber bands

Fabric square

Soft foam piece

Container

Balloon

Learning Targets

Students will ask questions and formulate hypotheses regarding the factors that affect the strength of electric forces

Students will conduct an investigation to provide evidence that fields exist between objects exerting forces on each other even though the objects are not in contact

Assessment

Student Self Assessment

During the kinesthetic modeling activity, ask students to describe in their own words how they knew when and how quickly to move towards particular electric charges in the model. They should describe explicit instances of cause and effect relationships in terms of attractive and repulsive electric forces. The facilitator can address conceptual misunderstandings and clarify where needed.

Peer Assessment

Students in each group test the effect of 3-6 different materials on the merry-go-round and explain to a partner the relative rates of spin. Then they collaboratively arrange the materials from left to right in terms of increasing electric force generated by the material. Students apply their learning to clarify concepts for each other with facilitator input where needed.

Teacher Assessment

Ask students to do/answer the following:

When using the static merry-go-round, describe instances where electric forces are repulsive and attractive. Students should correctly use the terms electric charge, electricfield, and magnitude in their description.

In what ways can the materials used in the static investigation be used to make predictions about the behavior of the merry-go-round?

Describe specific examples of how you might investigate the hypothesis you developed as part of this lesson. Be as specific as possible!

Students learn about electric current and voltage by exploring web resources on these topics and by engaging in virtual and hands-on activities. Students assemble their own series and parallel circuits by manipulating the arrangement of light bulbs connected to the battery pack. They observe the effect of each arrangement on the brightness of the bulbs as a relative measure of the electric forces affecting the movement of current through the circuit (MS-PS2-3).

Essential Questions:

What is a series circuit? What is a parallel circuit?

How does electrical energy move through a series circuit? How does this compare to parallel circuits?

LESSON PROCEDURE:

Prior Knowledge & Practice:

Student groups begin by watching a video on circuits, voltage, and current in the External Resources section. Write the following words on a whiteboard or flip chart. Direct students to pay attention to these terms while watching the video: switch, battery, potential energy, voltage, current, and series, and parallel. These terms are defined in the Concept Quick Review section below. If necessary, review these terms with students in more detail to clarify understanding.

Incandescent Light Bulb Component:

Twist the wires on two pre-stripped incandescent bulbs so they can be easily inserted through the holes in the schematic symbols.

Procedure:

Students build a circuit with only one bulb and connect it to the battery pack. Ask students to predict what will happen when the connections to the battery pack are switched. Connect the bulb to the battery and record observations in the Maker Journal page.

Add another bulb to the circuit and figure out where to connect the alligator leads so that the bulbs are connected in series. Students compare the relative brightness of the bulbs arranged in series to the brightness of one bulb connected to the battery pack. Record all observations in the Maker Journal.

Figure out how to arrange the circuit in parallel and compare the relative brightness of the bulbs in this configuration with observations of the circuit arranged in series.

Based on the learning from the video and activities, how do series circuits differ from parallel circuits in terms of the electrical energy moving through the bulbs? Discuss your ideas with your group and then write your own responses to the question in the Maker Journal page. Be sure to use the terms switch, battery, potential energy, voltage, current, and parallel.

T: Solicit prior knowledge on electrical circuits. “What is electricity? How does it move from place to place?”

S: “Electricity is power.” “It moves through wires!” “It flows through electrical components and then does stuff”

T: “Today we are going to explore these questions by using some resources and then engaging in a some fun activities. You will get a chance to build your own circuits!”

S: “What will we be building with today? How will we do it?”

T: “You will use materials in the materials station (provide them with a location) and use what you learn from the resources provided to build them. I will be providing assistance and suggestions when needed.”

Electricity is a form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current. An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma. Voltage, also called electromotive force, is the potential difference in charge between two points in an electric field, measured in volts. Batteries are common sources of voltage. Batteries consist of two oppositely charged electrodes. The positive end is a cathode and the negative end is the anode. Between the electrodes is an electrolyte solution through which electrons (charged particles) move from the cathode to the anode.

Battery: A battery contains stored potential chemical energy which is transformed into potential electrical energy. When the battery is connected to a bulb or motor (a load) the electrical energy can push/pull on the nearby electrons in the wires. A battery does not create electrons, but it does create a push/pull force on the electrons that are always present in the battery, wire, and bulb. The potential chemical energy in the battery decreases as more of the chemical energy is converted into electrical energy. To be accurate, 1-½ volt “batteries” should really be referred to as 1-½ volt “cells” as the chemistry involved creates a “push” (voltage) of 1-½ volts. A “battery” implies more than one cell. 6 and 9 volt batteries contain 4 and 6 of the 1-½ volt cells (4 x 1½ =6, 6 x 1½ =9, respectively).

Wires: Metals are conductors because some electrons in the metal can move about easily, unlike non-conductors (insulators) such as plastic and glass. Metals will vary in how easily electrons can move about (e.g. in how much the movement of electrons is resisted). Aluminum and copper are both metals with a low resistance to the movement of electrons. Copper is commonly used inside the wires found in homes and cars. Aluminum is used in some wires and is the basis for the folded foil wires as the foil can be easily cut, joined, and can be folded neatly. The foil wires from different ends of the battery must be kept from touching because the foil wires lack the insulated covering found on most other wires. Crossing the foil wires could lead to a short circuit, a very low resistance path from one end of the battery to the other. A short circuit can heat up the wire and battery and run down the battery.

Light Bulb: An incandescent bulb, such as the mini-holiday bulb, produces light when the wire filament inside becomes hot enough to glow. The filament contains the metal tungsten which has a relatively high resistance to the movement of electrons. When the bulb is connected to the battery, the electron movement occurs easily in the aluminum wires but is resisted in the coiled filament of the bulb. The friction from the resistance heats up the coil to over 2,000 degrees C (4,000º F). Heating energizes metal atoms and causes the atoms to vibrate or “jiggle”. When the atoms are hot enough these vibrating atoms can give off visible light. Light produced by heating is called incandescent light.

Switch: To turn the light on and off, a part of the circuit needs to be moveable so that the conductive path can be broken (separated) and reconnected as needed. A single pole, single throw switch is a switch with a single “on” position, as was constructed in the basic circuit. A hall light with 2 switches makes use of a more complex switch having 2 possible circuits and is called a double pole, double throw switch.

Breadboarding: The making of experimental circuits is called “breadboarding” and originally involved a breadboard! Most homes had a board for cutting bread, especially before sliced bread became commonly available. Early experimenters found the breadboard’s flat wooden surface an ideal nonconductive base for building electrical circuits. Early circuits used nails hammered into the board to create connection points for electrical components. This is why the term “breadboarding” has come to mean the easy and rapid creation of electrical circuits.

Series Circuits: When batteries are positioned with the positive end of one connected to the negative end of another, the batteries are said to be in series (“one after the other”). Batteries in series will provide more electrical push/pull, called voltage, than a single battery. Two 1-1/2 volt batteries in series can provide 3 volts to a circuit. Light bulbs, like the green ones in the picture below, can also be connected in series. Bulbs in series will glow less brightly than a single bulb in the same circuit as the 2 bulbs have to share the voltage.

Parallel Circuits: Batteries connected with the positive ends together and, separately, the negative ends connected together are said to be in parallel. The voltage remains unchanged but more potential chemical energy is available so the circuit can be powered longer. Bulbs connected so that each bulb has one lead connected to the positive battery end and the other to the negative battery end are said to be connected in parallel. Bulbs in parallel will glow as bright as a single bulb in the same circuit as long as the battery can supply the same voltage. Manufacturing differences can vary a bulb’s brightness.

Facilitator/Student Tutorials:

Steps to Building a Series Circuits

Set the two bulbs side by side on a flat surface. Connect the innermost wires using the ends of one alligator lead. The slack of the alligator lead wires can be wound and secured using short straw segments as shown if the extra wire makes the connections appear confusing.

Complete the circuit by connecting the power supply to the remaining wires on the bulbs.

Steps to Building Parallel Circuits

Connect alligator leads to one light bulb as shown in the picture (topmost light). Connect the remaining ends of these alligator leads to a second light bulb. Connect additional alligator leads to the second light bulb’s wires. Connect the battery holder to the alligator leads to complete the circuit.

Assessment

Student Self Assessment

Peer Assessment

Students demonstrate for each other how to build a series and/or parallel circuit and receive feedback from group members.

Teacher Assessment

Students review the web resources for this lesson and then create a poster depicting a series or parallel circuit that clearly and correctly indicates where electric currents vary in magnitude along the circuit. They will include text that summarizes how this demonstrates variation in the size of voltages (electric forces) in the circuit.

Students learn about the structure and importance of diodes in electrical circuits. They apply what they learn by engaging in a mini design challenge. Students will build a parallel circuit that includes two light bulbs and a diode and then figure out how to use the battery pack as an on/off switch for one of the bulbs. Students describe the affects of the diode in terms of the electric forces within the circuit (MS-PS2-3).

Essential Questions:

How do diodes affect the flow of electric current within a circuit?

What is the relationship between the position of a diode within a circuit and the configuration of the circuit?

LESSON PROCEDURE:

Students view the videos listed in the External Resources section in the right margin of this page and then answer the questions in the Maker Journal page as a team.

Students leverage their learning to build a parallel circuit that includes the diode component block, two light bulbs, alligator leads, and the battery pack on the large textured “egg crate” foam sheet. This is their prototyping breadboard. They may need to iterate several times in order to successfully light the bulbs.

When student teams successfully light both light bulbs in a parallel diode circuit, they draw it in the Maker Journal.

Ask this question: “Assume you cannot remove the diode or bulbs from your circuit. What change(s) can you make to the circuit to control the number of bulbs that light up? Have students discuss this quietly in their teams without sharing their ideas (they will share later).

Students reiterate and make the necessary changes to their circuits, maintaining the parallel configuration. When only one bulb lights up, students draw their modified circuits in the Maker Journal page, paying close attention to the schematic symbols and current flow (orientation of the battery pack).

Student teams discuss the role of the diode in both parallel circuits, citing specific attributes of the diode that allow it to block or allow current to flow and therefore affect the electrical forces within the circuit.

T: Show students pictures of a common diodes. You can find several pictures using Google Images. “What is the name of this electrical component? Has anyone seen these before?”

S: “Is it a resistor?” “It looks like a diode.” “I saw these on a computer motherboard before!”

T: “We are going to construct circuits that contain a special component called a diode. Diodes act as a one-way valve for electrical current in a circuit. You will be building circuits together in both series and parallel configurations that contain a diode and two light bulbs. You will have to discover the correct way to connect the diode within the circuit so that both bulbs light in one configuration and only one bulb lights in another configuration. I will not be telling you how to assemble the circuits, but you are already familiar with series and parallel circuits. Building on this knowledge and applying what we will soon learn about diodes, you will be successful!”

S: “A one-way valve only allows stuff to move one way, so if electrical current can only move one way through a circuit, the light bulb might not light.” “The current cannot flow backwards across the diode!”

T: “This is what you will soon find out. Remember to think about electrical current in terms of electrical forces pushing energy through the circuit. We will relate this concept to the role of the diode and its attributes (its characteristics that allow it to behave as it does). You will record your observations and ideas in the Maker Journal Page for the lesson.”

A diode is an electrical component that allows current to move through a circuit in only one direction. The most common kind of diode in modern circuit design is the semiconductor diode (see picture and schematic symbol below). When the polarity of a battery is such that electrons are allowed to flow through the diode, the diode is said to be forward-biased. Conversely, when the battery polarity is reversed, the diode blocks the current. The diode is said to be reverse-biased in this case. Diode behavior is similar to the behavior of a check valve. A check valve is pressure-operated and allows fluid to flow through it in only one direction. Diodes are essentially the same but instead are voltage-operated.

The essential difference between forward-bias and reverse-bias is the polarity of the voltage dropped across the diode. A forward-biased diode conducts current and drops a small voltage across it. If the battery’s polarity is reversed, the diode becomes reverse-biased, and drops all of the battery’s voltage. If we consider the diode to be a self-actuating switch (closed in the forward-bias mode and open in the reverse-bias mode), this behavior makes sense.

The forward-bias voltage drop exhibited by the diode is due to the action of the depletion region formed by the P-N junction under the influence of an applied voltage (see below). The P section of a diode contain positively-charged spaces, or holes. The N section contains electrons (negatively-charged) that are attracted to the holes in the P section. The attraction between the holes and electrons creates diffusion across the boundary between the P and N sections, making the P section more negative and the N section more positive. If no voltage is applied across a semiconductor diode, a thin depletion region exists at the P-N junction, preventing current flow. The depletion region is almost devoid of available charge carriers, and acts as an insulator. If voltage is applied with the correct polarity, the depletion region in the P-N junction shrinks and allows current to pass through and continue towards other paths within the circuit.

Facilitator/Student Tutorial:

There are many ways to connect a parallel circuit that includes light bulbs and a diode. Students can discover through inquiry that it is easier to first connect the lights in parallel without the diode. Encourage students to think about how multiple alligator clips can connect to the same point to form junctions. The diode can be added in such a way that it becomes one of the junctions. Then, students simply have to connect the clips on the diode junction so that at least one of the bulbs lights up.

Below is one example of how the parallel circuit may be connected. Notice how the lights are connected in parallel, with one bulb (circled) forming a junction that simultaneously connects to the battery pack, the other bulb, and to the diode. Similarly, the diode connects to the same components. Students must discover the appropriate places on the diode to connect the clips so that one bulb lights up. Switching between having one bulb or two bulbs illuminate can be done by changing the orientation of the diode (notice the bulb below in yellow box). This works but it is preferable to change the orientation of the battery pack instead because this provides a better example of the effect of reversing current through the diode and how diodes can serve as temporary switches in a circuit.

Students continue their learning on diodes by investigating light emitting diodes, or LEDs, and how they are used in electrical circuits. They will build series and parallel circuits with two LED-resistor component blocks and note the relative brightness of light emitted from the LEDs for each configuration. Students will troubleshoot and modify their circuits, making the necessary changes to ensure the electrical current is flowing the appropriate direction to illuminate the LEDs. Students identify and describe the path of the current through the circuit and explain their observations in terms of electrical forces (MS-PS2-3).

Essential Question:

What functions do LEDs serve in a circuit?

How can LEDs be used to describe electrical forces within a circuit?

LESSON PROCEDURE:

Student should watch the videos listed in the External Resources section in the right margin of this page. This will provide basic information on how LEDs work and why it is important to avoid applying voltages above the rating specified for certain LEDs, especially if no resistor is used.

The groups use two Resistor-LED component blocks to build series and parallel circuits (see Concept Quick Reference section below). They will likely need two of the 3V battery packs assembled earlier in the unit.

Students describe the flow of current through the circuit in terms of electrical forces and also describe the purpose of the LED in common devices. They record their findings in the Maker Journal Page for this lesson.

T: Show students pictures of several illuminated LEDs. You may find them using a Google search. Ask, “How are these lights different than the incandescent light bulbs used we used earlier?”

S: “Those are LEDs!” “They do not get hot like light bulbs.” “LEDs are so pretty!”

T: “Today we will learn about these lights, called LEDs, and the difference between them and the incandescent bulbs we typically associate with electric lights. Them we will build LED circuits in series and parallel in order to understand the behavior and how they function to control electrical forces within a circuit.”

S: “How many LEDs can we use in our circuits? Do we build the circuits with the same battery pack as before?”

T: “You must include two LEDs in your circuit. Find out what is possible with parallel and series LED arrangements in terms of voltage. This will require persistence and troubleshooting on your part! Relate these results to the observed brightness of the bulbs in each configuration. Are their noticeable relationships? Let’s see! This data can be used to determine the effects on the electrical forces within the circuit and provide insight into the overall function of LEDs.”

A light–emitting diode (LED) is a two-lead semiconductor light source. The schematic symbol for an LED is provided below. It is a p–n junction diode (see lessonGetting Directional with Diodes), which emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. The light emitted is usually monochromatic, meaning it consists of one single wavelength of light rather than being a combination of colors.

LEDs come in a variety of colors depending on the semiconducting materials used to form the p-n junctions. For example, aluminum gallium indium phosphide (AlGaInP) alloys are used for red, orange, and yellow LEDs while indium gallium nitride (InGaN) is used for green, blue, and white LEDs. Each LED color has a specific voltage requirement to cause it to light and an associated voltage drop (see below). Voltage drop describes the reduction of source voltage as electric current moves through the passive elements of an electrical circuit. Voltage drops across loads and across other active circuit elements are desired as the supplied energy performs useful work.

Building a circuit containing an LED usually requires the use of a current-limiting resistor to prevent burning out the LED because a small change in voltage across the LED can produce a large change in current. It is safer to include current-limiting resistors to achieve a target current, say 20 milli-amps, or 20 mA. Purchased LEDs usually specify a rating. For example, it might read “3.3V @ 20 mA typical”.

LEDs can be arranged in a circuit in parallel or series the same as incandescent lights. The difference is the voltage requirement for each configuration. For example, white LEDs usually require 3 volts, so two of them connected in series makes the voltage requirement for the circuit at least 6V (3V per LED). The same two LEDs connected in parallel would only require 3V to illuminate.

Facilitator/Student Tutorial:

LEDs connected in parallel and series behave much the same way as incandescent bulbs do in these same configurations. The difference is the amount of voltage needed to light the bulbs and the direction the current is moving through the circuit (they are diodes!). Below are examples of how to build a parallel circuit (left) and series circuit (right) using the Resistor-LED component blocks. Notice that in both circuits there are two battery packs connected in series. This provides six volts (6V) for the circuit, which is enough to light the bulbs in either configuration. Students should notice the difference in brightness (more dim for the series circuit). This is because of the voltage drop across each of the LEDs (explained above). The LEDs in series reduce the current flowing through the circuit, and this affects the amount of light emitted.

Lesson Materials

Building Materials

(Resistor + LED) component blocks, 2 (assembled earlier)

Alligator leads, 6

3V Battery pack, 2 (assembled earlier)

Tech

Computers or mobile devices

Internet access

External Resources

Maker Journal Pages

Teacher Notes

Encourage student groups to allow all group members to practice configuring the whole circuit or parts of the circuit. This will help all students reinforce their understanding that electric current direction is important to LED function. During the lesson students may get frustrated when one or no bulbs light, but this is a natural part of the learning. Encourage exploration without revealing the answers!

Learning Targets

Students will be able to build series and parallel circuits using LEDs and resistors

Students will be able to describe LED function in terms of current and electrical forces

Assessment

Student Self Assessment

Student groups review their Maker Journal pages and summarize their learning in a group discussion.

Peer Assessment

Student groups discuss and compare their findings and share any difficulties experienced with building the circuits, as well as provide feedback to peers that could solve these issues.

Teacher Assessment

Students demonstrate for the class how to build either a parallel or series circuit and then explain how the electrical energy from the battery is converted into light by the LEDs.

Students learn about resistance in a circuit and its importance in restricting the amount of current that can flow through various electrical components. Students read resistance color codes and use them to identify specific resistors on the Component Circle. Students practice calculating the total resistance for series and parallel circuits having up to two resistors and apply Ohm’s law to calculate the current flowing through the circuits. Students investigate the effects of series and parallel resistor configurations on the relative brightness of an LED, correlating calculations with their observations. Students explain their observations in terms of electric forces (MS-PS2-3).

Essential Questions:

What is the main function of a resistor in a circuit?

How does the effect of total resistance in a series circuit differ from that of a parallel circuit in terms of electric forces?

LESSON PROCEDURE:

What is Resistance?

Introduce students to the concept of electrical resistance by discussing the analogy where too many people try to go through a doorway at one time (see Student Directions below).

Show students the Resistor Animation video and ask them to describe voltage, current, and resistance in their own words based on learning from the video. Relate the door analogy to the resistor depicted in the animation.

Quick Write – Students write a paragraph in their Maker Journal student page using this sentence frame: “Resistors are important in a circuit because …” After 2-3 minutes, let students share their ideas with a partner or the whole class. Provide guidance and other ideas as needed to clarify understanding.

Resistance Color Codes

Show students an image of a circuit board containing different types of resistors. Explain that resistors vary in shape, size, and color. This lesson focuses on the typical “sausage-shaped” resistors that have colored bands on them. Ask students to identify this type of resistor in the image.

Display this image of a resistor. Have a student count the number of colored bands on the resistor.

Explain the bands as a method of labeling this type of resistor with the amount of resistance it produces in a circuit. Show them a resistor color code chart.

Students use the chart to confirm the value for the 4-band resistor in the Resistor + LED component block (1K = 1000 Ohms = Brown, Black, Red, Gold). After students try on their own, model how to use the chart to read the color code, pointing out the importance of the multiplier in determining the value.

Exercise – Students choose three resistors on the Component Circle for which to confirm values. After a few minutes, call on 1-2 students to share one resistor they chose, the resistance value, and a step-by-step description of how they used the chart to confirm the value. Continue as needed until students demonstrate proficiency using the chart.

Show students the Resistor Color Codes video for additional support or as an introduction to color codes.

Students practice calculating equivalent resistances for series and parallel connections using the resistance values listed in the Maker Journal page. Remind them to pay attention to both the number value and symbol for the values. For example, 47K is 47,000 Ohms whereas 100K is 100,000 Ohms. This is different than 47R, which is just 47 Ohms. The letter R means ohm. Numbers coming before the R indicate a value more than one. For example, 1R = 1 ohm; 47R = 47 ohms; and 4R7 = 4.7 ohms (used as a decimal in this case). Any numbers coming after the R indicate a value less than one, so R56 means 0.56 ohms.

Show students the video on Ohm’s Law as applied to LED circuits. After the video, write the equation V = IR on the board. Have students solve this equation for current (I) and then calculate the current for each of their equivalent resistance calculations conducted earlier (assume a voltage of 3V). Provide assistance as necessary.

Investigation – The Effects of Series and Parallel Resistor Configurations on LED Brightness

Each student group will use the 3V battery pack, Resistor + LED component block, and Component Circle assembled earlier in the unit.

Explain to students they will be using the different resistors on the Component Circle during the investigation but they will NOT need to be removed from the foam.

Students first build a simple circuit as shown below and calculate the current flowing through the circuit, given the 1K resistor and 3V supply. They observe the brightness of the LED on the component block. This calculated current and brightness will serve as a control for the investigation.

Next, students choose a resistor from the Component Circle and connect it in series with the resistor on the component block (shown below). They calculate the equivalent resistance and the current flowing through the circuit, recording the values and observed effect on the LED brightness in the Maker Journal page.

Students connect the same resistor in parallel with the resistor on the component block and again calculate and record equivalent resistance, current, and the effect on the LED.

Students continue this procedure for three more R-value resistors and three more K-value resistors on the Component Circle, trying to choose resistors at the ends and middle of the range of values.

Note: It is worth mentioning to students that using the different resistors on the Component Circle is much like using a variable resistor, or varistor, that can be adjusted to different relative levels of resistance (see Concept Quick Reference below). The advantage of the Component Circle is that students know the resistance values, which would not be possible when using a varistor unless they use a multimeter to measure resistance across the varistor.

T: “What does it mean to resist something? If I say I want to resist certain foods, what am I saying?”

S: “You are saying you do not want to be near the foods.” “Resistance means to stop or slow something down!”

T: “That’s right. Now let’s think about it this way. Suppose we all try to go through the door at one time. Will any of us get through? Probably, but some of us may just get stuck. If this happens, how might we get stuck people through the door?”

S: “We can push them through really hard!” “If we get through, we can help pull stuck people out to the other side.”

T: “Yes! The doorway resists letting us all go through at one time but we can push or pull more people through, sort of helping them along. In electrical circuits, electric charges (electrons) move through conductive wire much like people through the door in our analogy. The resisting “doorway” is a component called a resistor that restrict how many charges flow around the circuit each second. The pushing and pulling force that moves the charges through the circuit, and therefore through the resistor, is due to voltage supplied by the batteries we’ll use in today’s lesson.”

Resistance Color Codes

T: Show students the circuit board image. “What do you see in this picture? Where are the resistors?”

T: “Resistors can have different sizes and shapes, but most of the ones we’ll see and use are shaped like little sausages (image). Notice the colored bands on this resistor. How many bands do you see? These tell us how much resistance this component provides a circuit.”

S: “I see five bands!” “Why don’t they just print the resistance onto the resistor?”

T: “These components can be very small, making printing difficult to write on them as well as to read. We’re going to look at the color code chart, which helps us read the colored bands on resistors. Look at the Resistor + LED component block we assembled earlier in the unit. Use the chart to confirm the color code represents a resistance of 1000 ohms (1K). We’ll practice this process with other resistors as well.”

Calculating Total (Equivalent) Resistance and Applying Ohm’s Law

T: “Look at this image. What do you think the total resistance for this series circuit is and why do you think that?”

S: “I think you just add them together.” “I think it’s half of the values shown.”

T: “Choose a partner, then think, discuss, and share your ideas for knowing the total resistance in this circuit.”

S: “We think that you can figure the total resistance by …”

T: “Now look at this image of a parallel circuit. Discuss how you would find the total resistance for this circuit with a different partner.”

S: “We believe you would divide the sum of the resistances by 2 to get an average.”

T: “Let’s watch a video that explains how to figure this out, then we’ll reflect on what we learned and do some calculations using resistance values in the Maker Journal. Afterwards, we’ll learn about Ohm’s Law and apply it to our calculations.”

The electrical resistance of a material is a measure of how easily electric charge flows through the material. This resistance, R, is defined as the ratio of of the voltage across the material to the electric current flowing through it. Mathematically, this relationship is written as R = V / I. The SI unit for resistance is the ohm named after Georg Simon Ohm. One ohm is 1 volt per 1 ampere. If the material has low resistance, more current can flow through it for a given voltage. The equation R = V / I can be rewritten as the more familiar V = IR, known as Ohm’s Law. It is not really a physical law but an empirical statement about the behavior of materials.

Resistors are electrical components made of materials that have specific resistance values. They are connected in a circuit by conducting wires assumed to have negligible resistance. In schematic diagrams, resistors are represented with zigzag lines. When two or more resistors are connected in series, current moves through one resistor and is reduced before it moves through subsequent resistors in the series, producing a cumulative effect on the electric current flowing through the circuit. This is called total or equivalent resistance and is mathematically expressed as R(eq) = R1 + R2 + … + Rn, for n resistors connected in series.

For resistors connected in parallel, the total (equivalent) resistance can be found using the formula 1/R(eq) = 1/R1 + 1/R2 + … + 1/Rn. Notice that each term is written as one over the resistance value. This has implications for the total resistance in the circuit. For example, in circuits that only have resistors connected in parallel the equivalent resistance will be less than the lowest resistor value in the circuit. This can be explained by the idea that in a parallel connection, current has more paths that it can flow through to reach the terminals of a battery. The more paths available, the less resistance experienced by the charges moving through the circuit. This is also why lights connected in parallel shine the same no matter how many lights are included in the circuit.

Resistors are characterized by their resistance values and their power ratings, measured in watts. The power rating indicates the amount of power the resistor can tolerate without being damaged due to overheating. Remember that a resistor’s material slows down electric current being “pushed” through it by the voltage. The electrons are moving and as they slow down they lose kinetic energy (energy of moving objects). The lost energy has to go somewhere or be converted to other types of energy, like heat, which can burn up a resistor depending on its power rating. Do I smell toast?!

Lesson Materials

Building Materials

LED + Resistor component block

Rectangle “egg crate” foam sheet

Component Circle

3V battery pack

Connecting Materials

Alligator clips

Tech

Computers or mobile devices

Internet access

External Resources

Maker Journal Pages

Teacher Notes

Monitor student calculations for equivalent (total) resistance, especially for resistors connected in parallel. A common error is to forget that each term in the equation for resistors in parallel is an inverse: 1/R(total) = 1/R1 + 1/R2 + … + 1/Rn. Students need to understand this to make sense of their observations during the investigation. For resistors in series the calculation usually does not pose a problem for students: R(total) = R1 + R2 + … + Rn.

Learning Targets

Students will be able to investigate the effects of having two resistors connected in series and parallel and calculate equivalent resistance for both configurations

Students will use this understanding to determine how the arrangement of resistors affects the strength of electric forces in the circuit by calculating the current flowing in the circuit using Ohm’s Law.

Assessment

Student Self Assessment

Students review their calculations for equivalent resistance and current and then summarize their learning in a group discussion

Peer Assessment

Students listen to and build upon the explanations from peers on the correlation between resistor arrangement in a circuit and relative LED brightness observed during the investigation

Teacher Assessment

Problem: Suppose we need a circuit with two resistors connected in parallel. We want a total resistance of 956 ohms and one of the resistors has a value of 1000 ohms (1K). What is the value of the second resistor? Explain why an LED connected in this circuit would be less bright if the resistors were connected in series rather than in parallel.

Students learn about the basic structure of a capacitor and its role in storing electrical energy. They build a simple circuit that includes a capacitor and investigate the charge time for the capacitor. Then students reconfigure the circuit to investigate how long the capacitor will power an LED (discharge time). Students connect capacitors in series and parallel and calculate the total (equivalent) capacitance for the circuit in each instance and measure the average discharge times for each equivalent capacitance and then correlate their observations with the calculations. Students use the resources in the lesson and their observations to describe how capacitors can affect the electric forces in a circuit (MS-PS2-3).

Essential Questions:

What is a capacitor and what is its purpose in a circuit?

What is the effect of arranging capacitors in series versus parallel in terms of total capacitance? In terms of charging and discharging times?

How does the arrangement of the capacitors in the circuit affect the electric forces in the circuit?

LESSON PROCEDURE:

What are Capacitors?

Have students provide examples of how energy is stored and why it is stored. Lead them towards thinking about energy in various forms such as chemical energy in stored in food, potential energy stored in a stretched rubber band, and electrical energy stored in a battery (see Student Directions below).

Show students the Capacitor Animation video and ask them to describe what is happening in their own words and then share their ideas. Key things to ask while listening to student descriptions include: Where is charge being stored in the circuit? Which component is the capacitor? Why did the video show the inside of the capacitor? What did they show happening on the inside before and after charging? What happened to the stored charge?

Play the Capacitor and Capacitance video. Students answer the questions in the Maker Journal page, asking clarifying questions as needed. They should pay close attention to details regarding the description of capacitance, how capacitors are charged, the effects of larger or smaller forces on the electrons, and ways of increasing the capacitance in a capacitor.

Types of Capacitors

Show students an image of different capacitor types. Explain that capacitors vary in shape, size, and color just as resistors do. Examples to focus on are the orange ceramic capacitors and the barrel-shaped electrolytic capacitors. Most of the capacitors they will use later in the lesson are this type.

Ask a student to read the printing on the side of the large blue capacitor in the image. Explain that the units for capacitance are called farads but most values are listed as microfarads (uF), that is, 10^-6 farads (10 raised to the negative 6th power). The printed value of the large blue capacitor 4700uF. Ask students how many volts are listed on the capacitor. They should see that it is 35V. Ask them what this means based on the videos (Answer: maximum voltage the capacitor should be exposed to and can store safely).

Capacitor Charging Time Investigation

Students assemble the first circuit shown below using the 100uF Capacitor component block, the Resistor + LED component block, and two 3V battery packs (assembled earlier in the unit).

Students draw the circuit and write a hypothesis on what they will observe when they connect the alligator clips to close the circuit in the Maker Journal page.

Students close the circuit and record the amount of time in seconds for the LED to go out. Students repeat the procedure two more times and calculate an average charging time for the 100uF capacitor.

Students choose two more capacitors from the Component Circle and conduct the investigation again, calculating an average charging time for each value chosen. Note: Students may need to experiment with different capacitor values to find values that yield results they can observe, e.g. some capacitors may charge too fast for students to obtain a time measurement.

Capacitor Discharging Investigation

Students have charging time data for three capacitors. Now they will assemble the second circuit shown below using the 100uF Capacitor component block.

Students draw the circuit and write their hypothesis in the Maker Journal page regarding what they will observe when they disconnect the batteries and close the circuit, leaving the capacitor as the power source.

Students conduct the investigation and record the time in seconds required for the LED to go out. They repeat this process two more times and calculate the average discharge time for the 100uF capacitor.

Students repeat the procedure for the two other capacitors for which they have time data.

After the investigation, students answer the questions in the Maker Journal page.

Investigating Equivalent Capacitance in Series

Show students the video for capacitors connected in series. Write the equation for equivalent capacitance in series on the board: 1/Ceq = 1/C1 + 1/C2 + … + 1/Cn. Remind students that each term in the equation is an inverse of the individual capacitance value!

Students use the capacitance values for two of the capacitors investigated earlier and practice calculating the equivalent capacitance in series, recording their work in the Maker Journal page. Then, students hypothesize about the relationship between the discharge times of the individual capacitors and the equivalent capacitance.

Students follow the schematic below to assemble a circuit with two capacitors arranged in series. They will use the capacitors they chose for the calculation above. Provide assistance as needed.

Students close the circuit to charge the capacitors. Note: Students should determine how long to keep the circuit closed, ideally based on the previous investigations, and keep the charging time consistent for this investigation.

Students open the circuit to discharge the capacitors, recording the time required for the LED to go out. They charge and discharge the capacitors two more times and then calculate an average discharge time for this circuit.

Students compare the results with their hypothesis on the relationship between discharge time and equivalent capacitance for a series capacitor arrangement.

Students use the same capacitors as before to calculate equivalent capacitance in parallel.

Students follow the schematic below to assemble a circuit with two capacitors arranged in parallel.

Students close the circuit to charge the capacitors, again keeping the charging time consistent.

Students open the circuit to discharge the capacitors, recording the time required for the LED to go out. They charge and discharge the capacitors two more times and then calculate an average discharge time for this circuit.

Students analyze the relationship between discharge time and equivalent capacitance for a parallel arrangement.

S: Answers will vary – “Batteries store energy!” “We get energy from food, so it must be in there.”

T: “Yes, and also think about a stretched rubber band. They store potential energy, or energy that has the potential to do work on other objects. That’s why we don’t shoot stretched rubber bands at our neighbors! Now, we’re going to watch a video animation on an electrical component called a capacitor. I want you to think about these questions – Where is charge being stored in the circuit? Which component is the capacitor? Why did the video show the inside of the capacitor? What did they show happening on the inside before and after charging? What happened to the stored charge?”

S: “Charge is stored on the walls of the capacitor.” “The charge went through the light bulb and turned it on!”

T: “We’re going to watch another video that explains capacitance in more detail. Pay close attention to things like what capacitance is, how capacitance can be increased, and what is happening in a capacitor in terms of charge and forces.”

T: “Capacitors vary in terms of color, size, and shape just as resistors can have various designs. Notice there are disc-shaped ones along with others that look like barrels. Those will be the ones we work with the most in this lesson. Look at the biggest one. What does it say on its side?”

S: “It says 4700uF, 35V. I know what volts are but what does uF mean?”

T: “That stands for microfarads. The unit of capacitance is called a farad, named after a scientist. They are big units so with most electrical components the values are written on the sides in uF or a special number code. Based on what you learned so far, why would the makers of this capacitor write 35V on the side? What does this mean for the capacitor?”

Capacitor Charging Time Investigation

T: “We’re going to investigate how long in takes for a capacitor to charge. We’ll use the 100 uF component block as well as the Resistor + LED block we used in previous lessons. We’ll use two battery packs.”

S: “How will we know how to build the circuit?”

T: “You will use this picture (schematic) to assemble the circuit. Notice the location of the switch and the polarity of the batteries as well as the capacitor and LED. This is important. Draw the circuit in the Maker Journal page and write your hypothesis about what you expect to happen when the circuit is closed (connected). Afterwards, close the circuit. What did you see?”

S: “The LED was lit and then went out! Is that good?”

T: “Yes, that means the capacitor was charging and then stopped because it was fully charged. The next step is to determine how long it takes to charge. Do this by closing the circuit and recording the time for the light to go out. You will do this three times and average the times for the 100 uF capacitor.”

S: “Will we use other capacitors?”

T: “Yes! Choose two capacitors from the Component Circle and then do the procedure again, remembering to take three measurements and take an average for each capacitor. These capacitors will be used again in this lesson.”

Capacitor Discharging Time

T: “We investigated the charging times for three capacitors. Now let’s investigate how how long it takes to discharge them. Draw the circuit shown here in your Maker Journal page and write your hypothesis about what you’ll observe based on what you learned so far.”

S: “Will the battery packs be disconnected from the circuit? It seems we need to do that so the capacitor is the power for the circuit.”

T: “Absolutely! This circuit design makes it easy based on where the switches are located. Your group will need to use your findings from the last investigation to charge the capacitor for the appropriate amount of time and then stick to that charging time throughout this investigation.”

S: “Can you run quickly through the procedure please?”

T: “Start with the 100 uF capacitor, close the circuit to charge the capacitor, close the circuit to power the light with the capacitor, and record the discharge time (seconds for LED to go out). Do this two more times, take an average, and repeat for the remaining two capacitors.”

Investigating Equivalent Capacitance in Series

T: “We investigated charge and discharge times for circuits having only one capacitor. Now we’ll look at the effect of having two capacitors in the circuit. What are the two basic circuit configurations or arrangements?”

S: “Parallel and series!”

T: “Yes, and just as resistors can be arranged this way, so can capacitors. But we do not know for sure how this will affect the time the LED will remain lit, that is, how long the two capacitors together can power the LED.”

S: “How will we know how to calculate the total capacitance? Is it similar to the equations for the resistors?”

T: “Yes, except there are differences between the two cases. Let’s focus on series arrangements and watch this video. How is the method shown here different than with resistors?”

S: “The equation for total capacitance in series looks like the equation for total resistance in parallel!”

T: “You got it! We’ll discuss why that is later. For now, draw this circuit in the Maker Journal page. Then, choose two of the capacitors we have worked with so far and calculate the total capacitance in series. Use your data from previous investigations to determine a time for charging these capacitors in series. Build the series circuit and go through the procedure we’ve been using for getting an average discharge time.”

S: “Will we change capacitors as before?”

T: “No, but you will hypothesize about how the discharge time relates to the arrangement of the circuit in terms of equivalent capacitance. In other words, how are your calculations related to your observations?”

Investigating Equivalent Capacitance in Parallel

T: “The next investigation is for capacitors arranged in parallel. What do you anticipate the equation for this arrangement will look like?”

S: “I think it will look like the total resistance for resistors arranged in series.”

T: “You’re right! Let’s see an example in this video. Afterwards you will use the same capacitors used in the series circuit and calculate the equivalent capacitance, draw and build the circuit, and then run through the procedure again to determine the average discharge time for the arrangement.”

Capacitors are electrical components that maintain a potential difference (voltage) by storing charge. They control the storage and delivery of charge within electrical circuits. It takes energy to separate charges and maintain a potential difference, so capacitors are said to store energy. This energy can be seen as electrical discharges resulting in sparks. The amount of charge a capacitor can store depends on the design of the capacitor and the amount of voltage applied to the capacitor. The more voltage applied to the capacitor, the more charge it can store and thus release when discharged. Capacitance is measured in units called farads (F), which are mathematically represented as charge in coulombs (C) per volt (V), or 1 F = 1 C/V. For prototyping on breadboard it is more practical to use capacitors with values in microfarads (uF).

The basic structure of a capacitor is relatively simple. Two metal conducting plates are separated by either air or another material called a dielectric (see below). Dielectrics are materials that do not conduct electricity but have an effect on the external electric fields in which they are placed. They protect against the possibility of charge leakage or accidental sparking across the plates. In the image below the plates have a specific area A and are separated by a dielectric with thickness d.

Capacitors do not always look nice and flat like the image above. in fact, many of them in use on computer motherboards and other electrical devices are cylindrical in shape (below). The metal plates are separated by a dielectric, rolled up, and then surrounded by an insulating material. Again, the amount of charge a capacitor can maintain depends on the area of the metal conducting plates, the amount of separation (distance) between the plates, and the nature of the dielectric between the plates.

Circuit boards such as computer motherboards usually have several capacitors arranged in series and/or parallel depending on the position on the board and specific function within individual circuits on the board, shown below.

Whether capacitors are arranged in series or parallel has an effect on the amount of electrical energy that can be stored. To understand this it is helpful to look at an example of the mathematics describing the total capacitance for each arrangement. The table below contains the equations for capacitors arranged in series and parallel.

Notice the total, or equivalent, capacitance for a parallel arrangement is simply the sum of the capacitance for the individual capacitors, that is, Ct = C1 + C2. Example: Suppose a circuit had capacitors in parallel with values 47 and 220 microfarads (uF). The equivalent capacitance would be Ct = 47uF + 220uF = 267uF. When capacitors are arranged in series the values are inverses, that is, they are calculated as 1/n where n is the capacitance value. For example, the values above would yield a total capacitance (1/Ct) = (1/47uF) + (1/220uF) = 0.021uF + 0.0045uF = 0.025uF. This is a huge difference in total capacitance values and will produce a noticeable affect on the amount of time an LED stays lit in a circuit.

Lesson Materials

Building Materials

LED + Resistor component block

100 uF Capacitor component block

Rectangle “egg crate” foam sheet

Component Circle

Two 3V battery packs

Connecting Materials

Alligator clips

Tech

Computers or mobile devices

Internet access

External Resources

Maker Journal Pages

Teacher Notes

For capacitors arranged in parallel, the negatively-charged metal plates in the capacitors are arranged on one side of the circuit while the positively-charged plates are on the other. This artificially increases the area of both types of charged plates and therefore increases the total (equivalent) capacitance, hence for capacitors in parallel Ceq = C1 + C2 + … + Cn. A point of confusion for students is that for capacitors in series the effect is NOT cumulative the way it is for resistors in series. The structure of the equations for both components are similar but the cases in which they apply are opposite.

Learning Targets

Students will build circuits to investigate charge and discharge times for capacitors with different capacitance values

Students will build capacitor circuits in series and parallel and calculate total capacitance for each arrangement

Students will correlate discharge times and capacitance calculations for each circuit arrangement

Students will use their observations to describe how capacitors can affect electric forces in circuits

Assessment

Student Self Assessment

Students draw pictures of basic capacitors that have different capacitance values. For example, they might draw three capacitors, each having the same dielectric but having different widths (distance between the plates as a variable).

Peer Assessment

Student groups discuss and compare their capacitor designs and measurements

Teacher Assessment

Have students use their capacitors to demonstrate how the capacitor can be used to describe electric forces within a circuit.

This lesson will demonstrate that transistors function as an “On and Off” switch, and as an amplifier of electricity. Students will take part in a mini-design challenge to create a valve that can control air coming out of a balloon. Students will be introduced to the impact of transistors on modern technology including modern circuitry and computer processors, and play 20 question binary game. Unit will conclude with students creating a collage about transistor.

Essential Questions:

Modern devices such as TV, computers, phones all come in smaller sizes now, what are some reasons this is possible?

How does a transistor work as an amplifier of electric current? How does a valve work?

How does a transistor work as an on-off switch? how does a CPU work?

LESSON PROCEDURE

1. Introduction:

Activate student thinking by using “Transistor Introduction” Maker Journal. Using pictures of old and new electronic devices, demonstrate to students that gadgets they use have evolved significantly. Get students to understand that they have shrunk in size, and increase in power and functionality. Use the guiding question: What innovations have allowed for the changes in their devices?

Highlight the transistor is a major reason why devices have evolved. Show video on transistors up to 4:45. https://www.youtube.com/watch?v=OwS9aTE2Go4

2. Demonstrate transistors as an on-off switch (or valve):

Using the example of a water spigot near your school or “MakerJournal: Transistor as Valves,” demonstrate to students that a transistor works in the same way. Water from the pipe goes into the valve and is stopped, electrical current flowing into the collector end of a transistor is also stopped. Both are in the off position.

When we turn the knob on the valve, water flows out of the pipe, and out the hose. When the base part of the transistor is given a charge, electricity flows from the collector and out through the emitter. When water or electrons flow, it is in the “on” position.

3. Transistor as amplifiers

Demonstrate that by controlling the knob of a spigot, you can control the amount of water leaving the hose. Transistors work the same way with how much charged is added to the base.

3. Build a valve (Mini Design Challenge)

Using balloons and straws, have students create a device that can stop and start air from flowing.

4. Build A Simple Circuit to test your Transistor

Using “Maker Journal: Build A Simply Circuit to Test out a Transistor,” have students build a simple circuit with a transistor that can be turned on and off with their fingers.

5. Connecting transistors to computing.

Highlight that a computer processor is made up of millions of tiny transistors that allows electricity to be turned on and off. The ability to turn things from on to off is a binary system. Demonstrate how powerful binary systems are when it comes to processing information by playing the binary game– “Twenty Questions”.

Tell students you are thinking of a person, a place, or a thing, and they must figure it out, but they can only ask yes and no questions. Have student count how many questions until they have the right answer.

6. Assessment

Have students create and present a collage representing what they know about transistors. Using RAFT: Teacher’s Rubric to check for understanding.

Sample teacher and student dialog. Include reference to Maker Journal page and button to link to student maker journal page.

1. Introduction

T: I am going to show you pictures of some old devices like TV, radio, music players, phones. Older electronics and new electronics share the same principles of running a power through a circuit to work. What are some differences you noticed between these old electronics and what you might see today at home or at school?

S: They’re old. They look much bigger. They run on different media. They weren’t digital.

T: [Accept all answers] Yes that’s all true. What I want to point out is that things you use today has evolved and changed. Someone mentioned that these older machines were bigger. What innovations might have lead to their smaller sizes now?

S: They don’t use tape anymore. They electronics inside might have changed. The tv uses flatter screens now. Newer stuff is made from new materials like plastics, so they are thinner.

T: That’s all true. Like I mentioned earlier, old and new electronics operate in almost the same way, by using electricity to power your device so it can do something. One of the main reasons why these devices have gotten smaller is because the circuit boards have gotten smaller. One huge reason for that is because of a breakthrough in the transistor. Who has a guess on what a transistor is, and what it does?

S: They act as a doorway for electricity to flow. They transition the electricity.

T: Let’s watch the first 4.5 minutes of this video to understand the impact of the transistor, and understand a bit on what it does. We’ll go indepth on how it works later. [Show video]

2. Demonstrate transistors as an On-Off switch (or a valve):

T: The video was a good introduction to how a transistor works, but I think we need a better example that we might be all used to. Let’s go outside, there’s a water spigot somewhere that will demonstrate this. But on the way there, can someone remind how many parts makes up a transistor?

S: Well, according to the picture you have up in the classroom, a transistor looks like a box with three legs. One leg is called the collector, the middle leg is called the base, and other leg is called the emitter.

T: Great. I have that exact picture printed here as well. We’re going to use the water spigot here as an example of how the transistor work. So in a transistor, electricity flows into the collector. In the water spigot, this pipe carrying water is the collector, water is flowing into it. But is the water coming out at the end of this hose?

S: No

T: Why? What is stopping it?

S: That knob right there is turned off, so the water can’t get through.

T: Exactly. This knob, is called a valve, and like any valve, it works by letting things through or not. So on your transistor, that middle leg is called the base, and it’s exactly like the valve or the knob. When the water isn’t flowing, the spigot is in the off position. When the base is in the off position, no electricity flows through. It is stopped. What will it take for me to get water to the hose?

S: You have to turn the knob.

T: Exactly, what will it take for the base of the transistor to be turned on? It takes a charge of electricity. Once the base is given a mild charge, it is turned on, and electricity is allowed to flow to the emitter. Again, the emitter in this example is what?

S: It’s the hose.

T: When water flows from the pipe, through the valve, and out the hose, what position do we call this?

S: It’s in the “on” position.

T: How does electricity flow in the transistor?

S: It goes from the collector, through the base, and out of the emitter.

3. Transistor As Amplifiers

T: It was also mentioned in the video, that a transistor works as an amplifier. Does anyone know what amplifying means?

S: It means that you can boost up the signals. It can change it.

T: Exactly. Lets use this water spigot still as an example. Water pressure in the pipe is always the same. What can I do to change how water is coming out of that hose?

S: You can put your thumb on it. You can turn the knob to full blast.

T: Exactly. did I do anything differently on the pipe (or the collector end)? But I can control how water flows by controlling the knob. The transistor works the same way. Electricity in the collector end is the same, but by controlling the base, we can shape how electricity comes out the emitter end.

3. Build a valve

T: Okay class, we talked a lot today about how a transistor like a valve. A valve is something that opens and closes and allows substances to be stopped or allow them to move. We’re going to do a mini design challenge. We’re going to use a balloon, this is our collector, electrons have been collected here. Our challenge is to build something that can let air (or electrons) to pass out of the balloon, and that can also stop air from passing through.

4. Build a Simple Circuit with a Transistor

T: Now lets get back to building circuits. I am going to give you a handout, on it, there’s a picture of a simple circuit. With your group, and using the materials we have in our kit, build the circuit on the picture. When you build it, use the handout to write down the steps you took to build it. Write it as if you can give those steps to someone and it can help them build it without the picture.

S: How will we know if the transistor works?

T: Once you are done, the transistor can be turned on with your finger. Don’t worry, it won’t shock you. But damping your finger a bit, you can put your finger between the contact point, and the current should through to your finger and charge the base. What happens when the base part of a transistor is given a charge?

S: It is turned on, and electricity is allowed to flow.

5. Connecting transistors to computing.

T: It was also mentioned in the video, that transistors play a huge role in modern computing and technology. We can find transistor on any circuit board, but where else do transistors exist?

S: They are in the CPU, that is in every single computer device.

T: That’s right, the video mentioned that transistors helped not just to shape electrical devices but also helped to shape the world with computing. By acting as millions of On-Off switches, it has increased computing power throughout the world, but why does a couple of On-Off switches allow for so many of things that things we enjoy like smartphones, and computers, and games, and satellite navigation.

S: It just does.

T: Understanding that something is either “On or Off” , or if it is “A or B”, or if it is “Yes or No” is very important, and you do it every day without knowing it. You judge the distance of cars before you cross the street, and your brain makes a decision is it safe? Yes or No. You try to make a basket, and before you shoot, your brain asks is it close enough to shoot? yes or no? Then it asks, can my shot be blocked? Yes or no? Asking yes or no question helps us find information in a very powerful way. Does anyone have an example of a yes or no game?

S: Yes, we have played “Guess who?”, and that’s a game where you answer with yes and no.

T: We’re going to play a game very similar to that. I am going to think of a place in my head and write it down, and you can ask me only yes and no questions, you have 20 questions to figure out the place.

S: Great. Let’s do it.

T: Now that we have played the game, let’s reflect on it. Why is being able to tell if something is yes or no, or on and off, so powerful?

S: When you learn that something is yes, it eliminates other things. Like if you know the place you were thinking of is in California, then we know it is not in New York, or any other place outside of California.

5. Assessment

T: Class, we learned a lot today about the transistor. Let’s take 15 minutes, and create a collage. You can take do it the traditional way and find and draw pictures, or you can do it using a presentation software. But the point of the collage will be to summarized what we know about the transistor, what makes it up, how does it work, what are things that are in it. Be creative and have fun. We’ll do a share out after about your collage and what we learned about the transistor.

Lesson Materials

External Resources

“Transistors – The Invention That Change the World” by Real Engineering

Maker Journal Pages

Transistor Introduction: Machines Then and Now

Transistor as On-Off Valves

Build A Simply Circuit to test a Transistor

Teacher Notes

Be comfortable telling your students that as a teacher and as a human being, you don’t have all the answers. Most concepts, ideas, processes, and material specifications can be researched.

Normalize that failing is a way of learning that is common for all people, even professionals such as engineers, scientists, doctors, lawyers, and athletes. Have signage around the class that supports growth mindsets. Use acronyms such as First Attempt In Learning (F.A.I.L).

Allow students to work through challenges, even if it seems they are having a tough time. Reference criteria and constraints to students as guideline, rules, and instructions for their design, and refrain from giving too much clarification. Students will get it.

Active Classroom

Tips for success in an active classroom environment:

Encourage students to take on different roles within the group. Have students switch roles that might include materials coordinator, notetaker, presenter, builder. All students should be encouraged to think of themselves as problem-solvers.

Communication is critical in the design process. Students need to be allowed to talk, stand, and move around to acquire materials. Help students become successful and care for the success of others by asking them to predict problems that might arise in the active environment and ask them to suggest strategies for their own behavior that will ensure a positive working environment for all students and teachers.

Practice and predict clean-up strategies before beginning the activity. Ask students to offer suggestions for ensuring that they will leave a clean and useable space for the next activity. Students may enjoy creating very specific clean-up roles. Once these are established, the same student-owned strategies can be used every time hands-on learning occurs.

Learning Targets

MS-PS-3: Apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy transfer.

Students will apply prior knowledge to design, construct, and test a solution that transfers energy.

Students will apply prior knowledge to design, construct, and test a solution that can complete a circuit and manipulate the flow of electrons.

Students will understand that the mechanism of a transistor consists of a collector, a base, and an emitter.

Students will be able to build a simple valve.

Students will be able to connect transistors to binary computing.

Students will understand the impact of transistors on society.

Assessment

Peer Assessment

Student Peer-Assessment is built into the Engineering Design Process. Students working in groups access eachother through brainstorming, testing, and iterating.

Teacher Assessment

Review student makerspace journal pages for formative assessment and discuss with individual groups as they work.

Conduct a whole group discussion to allow all students to share, discuss and compare their learning about what are transistors, how they work, and how they have impacted society.

Use Teacher’s Rubric to check for understanding during assessment stage:

In the culminating project, students will be challenged to create a board game that triggers different lights and sounds. Using the prior knowlegde obtained in the empathy and define stages of the engineering design process, students will generate ideas and themes, build prototypes, test and reflect on whether their design meets and exceeds the criteria and contraints.

Allow students the ownership of creating their gameboard and gameplay from scratch, or use gameboards provided at RAFT.net to save time. Gameboard templates are also available online.

Essential Questions:

Can your group design a board game that uses circuitry to trigger lights and sounds?

What were you able to learn by testing your design? How can you use that knowledge to iterate your design?

How do you play this game? What will others learn from playing your game?

LESSON PROCEDURE

Introduce students to a real-world challenge and the engineering design process (empathy stage).

Allow students to brainstorm, and sketch ideas (Define and ideate stage).

T: We are going to conclude our lesson on electrical engineering with a design challenge. We are going to work as engineers and game designers to create a board game. Before we start, can I get a few examples of your favorite board games to play?

S: [Accept all answers.] Monopoly. Twister. Catan. Risk. Blokus.

T: What do you like about board games? What makes your favorite board game fun?

S: [Accept all answers.] You get to play with others. There’s always a winner. It gets your family together. It’s something to do when you are bored. It makes people talk. It makes people get up. It makes people think.

T: Yes, it’s a game. It’s supposed to be fun. There’s suppose to be a winner, and everyone should have a good time.

T: We will create a board game. You can use the template gaming board [see external resources], or you can create your entire board from scratch. But the criteria insist that on your game must use electronics and that certain landing spots must trigger a light to go off, or a sound to buzz.

S: Are there any other rules?

T: Yes, as game designers and engineers we have certain rules, and they are broken down into two categories, the criteria and the constraints. Can someone share what is the difference between the two types of rules (criteria, constraints)?

S: The criteria are the things you must have in your design. The constraints are things that limits your design.

T: The best way for us to learn more about the process is to take part in it. Your design challenge is: How can your group create a board game that triggers lights and sounds?

Criteria & Constraints

Remember, all engineers deal with criteria and constraints when engineering. Engineers design things using some rules about how the designs must behave or work. These rules are called criteria. Engineers can run out of materials, money, time to build, or space in which to build something. In other words there are limits on how something can be built. These limits are called constraints. The criteria and constraints for this challenge are below.

Criteria (design requirements)

Constraints (design limitations)

The board game must trigger three types of lights to go off.

The board game must trigger three different sounds to go off.

The board game must allow to at least 4 players.

The board game must be powered by batteries.

The board game can only be built with materials provided

The board game must be completed and tested in the given time

The board game can not have a win it all landing spot.

Ideate

Have students work in groups, and brainstorm then sketch out their game board and circuitry on paper. Ask students to label key components of their game and of the circuitry of theeir game. Explain to students their sketches will be a part of their journal, and will be used to mark down where the device needs improvement.

T: Let’s take a moment to talk to each other. Think about the challenge, the criteria and the constraints, and think about what your board game and your electric circuit board will look like.

S: [Give student 5 minutes to talk to each other.]

T: Okay, now let’s take 5-10 more minutes and draw out a sketch of what important components are needed in your circuit, and how those components will connect with one another, and how that all connects to your game board. Remember this sketch will be important later when we identify what might have failed, and what might need some improvements on.

S: We have too many ideas and no one is listening.

T: Let’s follow some important brainstorming rules. 1. One person talks at a time. 2. When sharing ideas, try to summarize your idea like a heading of a newspaper. 3. Write down every single idea. 4. Group all the ideas together on the commonality.

Prototype

If a makerspace is available at your site, the prototyping phase is most conducive in this environment. Alternatively, supplies from RAFT’s Electrical Engineering module can be presorted on a table so that students can easily see, take, and return materials. Have students select a materials manager to bring supplies and avoid any potential traffic jams in the classroom.

Display criteria and constraints rules somewhere visible to all students. Allow students 10-15 minutes of build time, and then 10 minutes of testing in front of the class. This structure works for classrooms with less space, limited the testing area. This encourages group presentation during the testing phase where everyone gets to see each group test and present their design.

Alternatively, allow for 20-25 minutes of combined build and testing time. This structure works for larger classroom with more available testing areas, and students who work better through self-organizing. In this model, students get to test freely as they build, and can go through more iterations.

T: Let’s take our sketches and start creating our prototypes. Remember, only the supply coordinator should make it up to get supplies. We’ll have 15 minutes to try create our first prototype. Don’t worry about if you can’t finish on time, remember it’s our first prototype but we’ll have a second iteration.

S: We can make anything we want.

T: Yes, but remember it has to fit into the criteria and the constraints.

S: What happens if we need help?

T: First ask your team members, then if your whole team still need a bit of help, let an adult know.

Test and Reflect on your Design

Testing can be done in groups with each group taking turns to present in class, this helps to build public speaking and is a fun way of learning that failure points in your device are completely a natural part of engineering. Testing can also be done during build time to reduce pressure and induce more participation. Have students come up to testing area, and demonstrate their completed circuit boards.

Guiding Question:

Was your circuit board completed? and closed? if so, how do you know?

At what point did your circuit board hit a fail point?

Can you explain to us the idea behind your board game, and how we are suppose to play it. What are some key features of your game?

T: Okay everyone, let’s stop for a moment and take some time to do a test of our devices. Remember testing in engineering really isn’t for a grade, it’s for us to understand how our device is working and how we can improve on it. Let’s get a group to come up and test their design.

S: Our design isn’t done yet, but here is how we planned it out with our sketch.

T: We understand that when a circuit is closed, it allows for electrons to flow, and it causes electricity. What steps are needed for your group to close the circuits?

S: We can connect all the wires so that it starts at the battery and goes around and finally connects back to the battery.

T: How were you able to get three different lights to go off?

S: We had to use different paths for them. And they went off when they were triggered by a switch, or a closing the circuit.

T: What are some things you learned in your testing that you want to improve on in your next design?

S: We want to make the speakers louder, and maybe change the pitch.

T: Take a moment to think about that, if you want to make the speaker louder, what needs to happen to your circuit? What needs to be added, what needs to change for this to happen?

T: Remember everyone this is a great first trial. We learned so much, and if we continue with finishing this game, what is important for us to fix. Let’s write that down in our journal, so we can continue our improvements.

The engineering design process is an iterative process. Through testing, and data collecting (or lessons learned) engineers recreate through several iterations the design changes progresses incrementally until a final solution is created. There are many examples of the engineering design process, but all will follow the same principles of understanding a problem, brainstorming ideas, prototyping a solution, testing the solution, and reiterating the process.

Open and Close Circuits

A closed circuit board has a pathway for electrons to flow without interruptions. With all wires attached properly, and connected to an energy source like batteries, a close circuit should allow for electrons to flow to lights, speakers, and all components of the board.

An open circuit board might have the pathway for election to flow, but there is a gap somewhere that stops the cyclical flow, and the components of the board will not operate. A switch allows us to turn on and off a device by either breaking the pathway of electrons in the off position or be reconnecting the pathway of electrons.

Design Challenge Materials

Building Materials

all materials supplied in RAFT’s Electrical Engineering Unit

Connecting Materials

all materials supplied in RAFT’s Electrical Engineering Unit

Tech

N/A

Other

Batteries

External Resources

Maker Journal Pages

Teacher Notes

Normalize that failing is a way of learning that is common for all people, even professionals such as engineers, scientists, doctors, lawyers, and athletes. Have signage around the class that supports growth mindsets. Use acronyms such as First Attempt In Learning (F.A.I.L).

Allow students to work through challenges, even if it seems they are having a tough time. Reference criteria and constraints to students as guideline, rules, and instructions for their design, and refrain from giving too much clarification. Students will get it.

Active Classroom

Tips for success in an active classroom environment:

Communication is critical in the design process. Students need to be allowed to talk, stand, and move around to acquire materials. Help students become successful and care for the success of others by asking them to predict problems that might arise in the active environment and ask them to suggest strategies for their own behavior that will ensure a positive working environment for all students and teachers.

Practice and predict clean-up strategies before beginning the activity. Ask students to offer suggestions for ensuring that they will leave a clean and useable space for the next activity. Students may enjoy creating very specific clean-up roles. Once these are established, the same student-owned strategies can be used every time hands-on learning occurs.

Learning Targets

MS-PS3-3: Apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy transfer.

Students will apply prior knowledge to design, construct, and test a solution that transfers energy.

Students will apply prior knowledge to design, construct, and test a solution that can complete a circuit and manipulate the flow of electrons.

Assessment

Student Self Assessment

Student groups review their makerspace journal and summarize their learning in a group discussion

Peer Assessment

Student groups discuss and compare their findings and share different critical uses for water and methods of freshwater transportation that they discover in their research. Students should also share the difficulties that they discovered in transporting freshwater.

Teacher Assessment

Review student makerspace journal pages for formative assessment and discuss with individual groups as they work.

Conduct a whole group discussion to allow all students to share, discuss and compare their findings around different critical uses for water and methods of freshwater transportation that they discovered in their research. Students should also share about the difficulties in transporting freshwater.

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